As a cutting tool used in a cutting process for a workpiece such as a metal, a tool described in JP 2010-94747 A (Patent Document 1) is known, for example. An insert used in the cutting tool described in Patent Document 1 includes an upper surface, a lower surface having a flank surface, a side surface having a rake surface, a cutting edge formed on a ridge line where the lower surface and the side surface intersect each other, and a screw insertion hole (through hole) extending from the upper surface to the lower surface. The insert is fixed to a tool body (holder) by inserting a clamp screw into the screw insertion hole.
In recent years, there is a demand for a cutting tool having a small machining diameter. For this reason, it is necessary to miniaturize an insert. In order to reduce a size of an insert, a through hole should be reduced in size, or a distance between a through hole and a cutting edge should be narrowed. However, in a case where a through hole is reduced in size, a screw is made thinner, so that fixing of a cutting insert to a holder may be unstable. Also, in a case where a distance between a through hole and a cutting edge to which a force is applied at a time of cutting is narrowed, strength of a cutting insert may be degraded.